SVG Path Interpolator

The SVG Path Interpolator produces point data representing interpolated values within an SVG path. This is handy when you need to calculate complex paths for animation or drawing APIs beforehand. Complex paths that include Bézier curves are converted to polygons with a configurable segment sampling size producing more points with greater precision or fewer points for speed. Polygon path data can be used to animate, draw or for hit detection in games.

Install

npm install svg-path-interpolator --save

or as a cli

npm install -g svg-path-interpolator

Usage

CLI

Create a config.json somewhere in your project. See the sample.config.json for configuration options.

{
  "joinPathData": false,
  "minDistance": 0.5,
  "roundToNearest": 0.25,
  "sampleFrequency": 0.001,
  "pretty": false,
  "prettyIndent": 0
}

Then from your terminal, type

svgpi ./path/to/config.json ./path/to/target.svg ./output/fileName.json

In the browser as a direct script embed (no-build process)

Copy all files in the lib/ directory to svg-interpolator/ on your web server then point a script tag to it.

<script src="../svg-interpolator/index.js"></script>

The SVGPathInterpolator will be defined as a global and can be used anywhere

<script type="module" defer>
  const { createInterpolator } = SVGPathInterpolator;
  const interpolator = await createInterpolator({
    joinPathData: true,
    minDistance: 0.5,
    roundToNearest: 0.25,
    sampleFrequency: 0.001,
  }, '../svg-interpolator/sax-wasm.wasm');
  
  // ------ Get the SVG as a Uint8Array Via fetch ----------
  const response = await fetch('./path-to-svg.svg');
  if (!response.ok) {
    return;
  }
  const bytes = new Uint8Array(await response.arrayBuffer());
  // -------------------------------------------------------
  // --------------- OR from a DOM element -----------------
  const svg = document.querySelector('svg.my-svg');
  const bytes = new TextEncoder().encode(svg.outerHTML);
  //--------------------------------------------------------
  const paths = interpolator.processSVG(bytes);
  console.log('Created', paths.length, 'paths');
</script>

In the browser as a dependency (bundler like webpack or rollup)

import { createInterpolator } from 'svg-path-interpolator';
// ...
const interpolator = await createInterpolator({
    joinPathData: true,
    minDistance: 0.5,
    roundToNearest: 0.25,
    sampleFrequency: 0.001,
  }, '../svg-interpolator/sax-wasm.wasm');
  
  // ------ Get the SVG as a Uint8Array Via fetch ----------
  const response = await fetch('./path-to-svg.svg');
  if (!response.ok) {
    return;
  }
  const bytes = new Uint8Array(await response.arrayBuffer());
  // -------------------------------------------------------
  // --------------- OR from a DOM element -----------------
  const svg = document.querySelector('svg.my-svg');
  const bytes = new TextEncoder().encode(svg.outerHTML);
  //--------------------------------------------------------
  const paths = interpolator.processSVG(bytes);

joinPathData

When joinPathData is true, all path data is joined in a single array as the output. When false, each path is separated by the path id attribute in a json object as the output. If no id attribute exists on the path, a unique id is created.

minDistance

minDistance is the minimum distance between the current and previous points when sampling. If a sample results in a distance less than the specified value, the point is discarded.

roundToNearest

roundToNearest is useful when snapping to fractional pixel values. For example, if roundToNearest is .25, a sample resulting in the point 2.343200092,4.6100923 will round to 2.25,4.5

sampleFrequency

sampleFrequency determines the increment of t when sampling. If sampleFrequency is set to .001 , since t iterates from 0 to 1, there will be 1000 points sampled per command but only points that are greater than minDistance are captured.

pretty (cli only)

When true, pretty creates formatted json output

prettyIndent (cli only)

Then number of spaces to indent when pretty is true

Examples

Animating output

See this pen for an example on animating a simple path.